Conventionally, gallium indium nitride (compositional formula: GaXIn1-XN, 0≦X≦1) has been used as a light-emitting layer for a light-emitting element that emits visible light of dark green, blue or the like (refer to Patent Document 1). Moreover, for example, it is shown that a Ga0.4In0.6N layer to which zinc (chemical symbol: Zn) is added (doping is carried out) having a large indium composition is useful as a material for emitting red light (refer to Patent Document 1).
The light-emitting layer is in some cases configured with not only a numerically single gallium indium nitride layer, but also a superlattice structure using numerically plural gallium indium nitride layers having different indium compositions (refer to Non-Patent Document 1). Moreover, for example, there is a technical example in which configuration is made of a multiple quantum well (abbreviation: MQW) structure in which a multi-layered unit that includes a well layer constituted by plural gallium indium nitride layers having a constant indium compositions and a barrier layer constituted by a gallium nitride (GaN) layer is laminated plural times (refer to Patent Documents 2 to 4 and Non-Patent Document 2).
As the MQW structure, in the case of forming the light-emitting layer by use of the plural well layers and the plural barrier layers, there are some cases in which the gallium indium nitride layers or the gallium nitride layers to which impurities are intentionally added (doping is carried out) for forming a light-emitting layer having excellent conductivity (refer to Non-Patent Document 3). As n-type impurities for the group III nitride semiconductor, such as gallium nitride, silicon (chemical symbol: Si, refer to Patent Document 5), germanium (chemical symbol: Ge), tellurium (chemical symbol: Te), and selenium (chemical symbol: Se) are exemplified (refer to Patent Document 6).